[PATCH 1/2 v2] tracing/function-graph-tracer: various fixes and features

From: Frederic Weisbecker
Date: Thu Jan 22 2009 - 20:05:10 EST


This patch brings various bugfixes:

_ Drop the first irrelevant task switch on the very beginning of a trace.
_ Drop the OVERHEAD word from the headers, the DURATION word is sufficient and will not
overlap other columns.
_ Make the headers fit well their respective columns whatever the selected options.

Ie, default options:

# tracer: function_graph
#
# CPU DURATION FUNCTION CALLS
# | | | | | | |

1) 0.646 us | }
1) | mem_cgroup_del_lru_list() {
1) 0.624 us | lookup_page_cgroup();
1) 1.970 us | }

echo funcgraph-proc > trace_options

# tracer: function_graph
#
# CPU TASK/PID DURATION FUNCTION CALLS
# | | | | | | | | |

0) bash-2937 | 0.895 us | }
0) bash-2937 | 0.888 us | __rcu_read_unlock();
0) bash-2937 | 0.864 us | conv_uni_to_pc();
0) bash-2937 | 1.015 us | __rcu_read_lock();

echo nofuncgraph-cpu > trace_options
echo nofuncgraph-proc > trace_options

# tracer: function_graph
#
# DURATION FUNCTION CALLS
# | | | | | |

3.752 us | native_pud_val();
0.616 us | native_pud_val();
0.624 us | native_pmd_val();


About features, one can now disable the duration (this will hide the overhead too
for convenient reasons and because on doesn't need overhead if it hasn't the duration

echo nofuncgraph-duration > trace_options

# tracer: function_graph
#
# FUNCTION CALLS
# | | | |

cap_vm_enough_memory() {
__vm_enough_memory() {
vm_acct_memory();
}
}
}

And at last, an option to print the absolute time:

//Restart from default options
echo funcgraph-abstime > trace_options

# tracer: function_graph
#
# TIME CPU DURATION FUNCTION CALLS
# | | | | | | | |

261.339774 | 1) + 42.823 us | }
261.339775 | 1) 1.045 us | _spin_lock_irq();
261.339777 | 1) 0.940 us | _spin_lock_irqsave();
261.339778 | 1) 0.752 us | _spin_unlock_irqrestore();
261.339780 | 1) 0.857 us | _spin_unlock_irq();
261.339782 | 1) | flush_to_ldisc() {
261.339783 | 1) | tty_ldisc_ref() {
261.339783 | 1) | tty_ldisc_try() {
261.339784 | 1) 1.075 us | _spin_lock_irqsave();
261.339786 | 1) 0.842 us | _spin_unlock_irqrestore();
261.339788 | 1) 4.211 us | }
261.339788 | 1) 5.662 us | }

The format is seconds.usecs
I guess no one needs the nanosec precision here, the main goal is to find when happened
the events on a cpu when the trace switches from one cpu to another.

ie:

274.874760 | 1) 0.676 us | _spin_unlock();
274.874762 | 1) 0.609 us | native_load_sp0();
274.874763 | 1) 0.602 us | native_load_tls();
274.878739 | 0) 0.722 us | }
274.878740 | 0) 0.714 us | native_pmd_val();
274.878741 | 0) 0.730 us | native_pmd_val();

Here there is a 4000 usecs difference when we switch the cpu.

Changes in V2:
_ Completely fix the first pointless task switch.

Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
---
kernel/trace/trace_functions_graph.c | 298 ++++++++++++++++++++++------------
1 files changed, 195 insertions(+), 103 deletions(-)

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 3c54598..66fc7b8 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -1,7 +1,7 @@
/*
*
* Function graph tracer.
- * Copyright (c) 2008 Frederic Weisbecker <fweisbec@xxxxxxxxx>
+ * Copyright (c) 2008-2009 Frederic Weisbecker <fweisbec@xxxxxxxxx>
* Mostly borrowed from function tracer which
* is Copyright (c) Steven Rostedt <srostedt@xxxxxxxxxx>
*
@@ -21,9 +21,11 @@
#define TRACE_GRAPH_PRINT_CPU 0x2
#define TRACE_GRAPH_PRINT_OVERHEAD 0x4
#define TRACE_GRAPH_PRINT_PROC 0x8
+#define TRACE_GRAPH_PRINT_DURATION 0x10
+#define TRACE_GRAPH_PRINT_ABS_TIME 0X20

static struct tracer_opt trace_opts[] = {
- /* Display overruns ? */
+ /* Display overruns? (for self-debug purpose) */
{ TRACER_OPT(funcgraph-overrun, TRACE_GRAPH_PRINT_OVERRUN) },
/* Display CPU ? */
{ TRACER_OPT(funcgraph-cpu, TRACE_GRAPH_PRINT_CPU) },
@@ -31,17 +33,22 @@ static struct tracer_opt trace_opts[] = {
{ TRACER_OPT(funcgraph-overhead, TRACE_GRAPH_PRINT_OVERHEAD) },
/* Display proc name/pid */
{ TRACER_OPT(funcgraph-proc, TRACE_GRAPH_PRINT_PROC) },
+ /* Display duration of execution */
+ { TRACER_OPT(funcgraph-duration, TRACE_GRAPH_PRINT_DURATION) },
+ /* Display absolute time of an entry */
+ { TRACER_OPT(funcgraph-abstime, TRACE_GRAPH_PRINT_ABS_TIME) },
{ } /* Empty entry */
};

static struct tracer_flags tracer_flags = {
/* Don't display overruns and proc by default */
- .val = TRACE_GRAPH_PRINT_CPU | TRACE_GRAPH_PRINT_OVERHEAD,
+ .val = TRACE_GRAPH_PRINT_CPU | TRACE_GRAPH_PRINT_OVERHEAD |
+ TRACE_GRAPH_PRINT_DURATION,
.opts = trace_opts
};

/* pid on the last trace processed */
-static pid_t last_pid[NR_CPUS] = { [0 ... NR_CPUS-1] = -1 };
+

static int graph_trace_init(struct trace_array *tr)
{
@@ -154,17 +161,25 @@ print_graph_proc(struct trace_seq *s, pid_t pid)

/* If the pid changed since the last trace, output this event */
static enum print_line_t
-verif_pid(struct trace_seq *s, pid_t pid, int cpu)
+verif_pid(struct trace_seq *s, pid_t pid, int cpu, pid_t *last_pids_cpu)
{
pid_t prev_pid;
+ pid_t *last_pid;
int ret;

- if (last_pid[cpu] != -1 && last_pid[cpu] == pid)
+ if (!last_pids_cpu)
+ return TRACE_TYPE_HANDLED;
+
+ last_pid = per_cpu_ptr(last_pids_cpu, cpu);
+
+ if (*last_pid == pid)
return TRACE_TYPE_HANDLED;

- prev_pid = last_pid[cpu];
- last_pid[cpu] = pid;
+ prev_pid = *last_pid;
+ *last_pid = pid;

+ if (prev_pid == -1)
+ return TRACE_TYPE_HANDLED;
/*
* Context-switch trace line:

@@ -232,9 +247,34 @@ trace_branch_is_leaf(struct trace_iterator *iter,
return true;
}

+/* Signal a overhead of time execution to the output */
+static int
+print_graph_overhead(unsigned long long duration, struct trace_seq *s)
+{
+ /* If duration disappear, we don't need anything */
+ if (!(tracer_flags.val & TRACE_GRAPH_PRINT_DURATION))
+ return 1;
+
+ /* Non nested entry or return */
+ if (duration == -1)
+ return trace_seq_printf(s, " ");
+
+ if (tracer_flags.val & TRACE_GRAPH_PRINT_OVERHEAD) {
+ /* Duration exceeded 100 msecs */
+ if (duration > 100000ULL)
+ return trace_seq_printf(s, "! ");
+
+ /* Duration exceeded 10 msecs */
+ if (duration > 10000ULL)
+ return trace_seq_printf(s, "+ ");
+ }
+
+ return trace_seq_printf(s, " ");
+}
+
static enum print_line_t
print_graph_irq(struct trace_seq *s, unsigned long addr,
- enum trace_type type, int cpu, pid_t pid)
+ enum trace_type type, int cpu, pid_t pid)
{
int ret;

@@ -242,35 +282,40 @@ print_graph_irq(struct trace_seq *s, unsigned long addr,
addr >= (unsigned long)__irqentry_text_end)
return TRACE_TYPE_UNHANDLED;

- if (type == TRACE_GRAPH_ENT) {
- ret = trace_seq_printf(s, "==========> | ");
- } else {
- /* Cpu */
- if (tracer_flags.val & TRACE_GRAPH_PRINT_CPU) {
- ret = print_graph_cpu(s, cpu);
- if (ret == TRACE_TYPE_PARTIAL_LINE)
- return TRACE_TYPE_PARTIAL_LINE;
- }
- /* Proc */
- if (tracer_flags.val & TRACE_GRAPH_PRINT_PROC) {
- ret = print_graph_proc(s, pid);
- if (ret == TRACE_TYPE_PARTIAL_LINE)
- return TRACE_TYPE_PARTIAL_LINE;
+ /* Cpu */
+ if (tracer_flags.val & TRACE_GRAPH_PRINT_CPU) {
+ ret = print_graph_cpu(s, cpu);
+ if (ret == TRACE_TYPE_PARTIAL_LINE)
+ return TRACE_TYPE_PARTIAL_LINE;
+ }
+ /* Proc */
+ if (tracer_flags.val & TRACE_GRAPH_PRINT_PROC) {
+ ret = print_graph_proc(s, pid);
+ if (ret == TRACE_TYPE_PARTIAL_LINE)
+ return TRACE_TYPE_PARTIAL_LINE;
+ ret = trace_seq_printf(s, " | ");
+ if (!ret)
+ return TRACE_TYPE_PARTIAL_LINE;
+ }

- ret = trace_seq_printf(s, " | ");
- if (!ret)
- return TRACE_TYPE_PARTIAL_LINE;
- }
+ /* No overhead */
+ ret = print_graph_overhead(-1, s);
+ if (!ret)
+ return TRACE_TYPE_PARTIAL_LINE;

- /* No overhead */
- if (tracer_flags.val & TRACE_GRAPH_PRINT_OVERHEAD) {
- ret = trace_seq_printf(s, " ");
- if (!ret)
- return TRACE_TYPE_PARTIAL_LINE;
- }
+ if (type == TRACE_GRAPH_ENT)
+ ret = trace_seq_printf(s, "==========>");
+ else
+ ret = trace_seq_printf(s, "<==========");
+
+ if (!ret)
+ return TRACE_TYPE_PARTIAL_LINE;
+
+ /* Don't close the duration column if haven't one */
+ if (tracer_flags.val & TRACE_GRAPH_PRINT_DURATION)
+ trace_seq_printf(s, " |");
+ ret = trace_seq_printf(s, "\n");

- ret = trace_seq_printf(s, "<========== |\n");
- }
if (!ret)
return TRACE_TYPE_PARTIAL_LINE;
return TRACE_TYPE_HANDLED;
@@ -289,7 +334,7 @@ print_graph_duration(unsigned long long duration, struct trace_seq *s)
sprintf(msecs_str, "%lu", (unsigned long) duration);

/* Print msecs */
- ret = trace_seq_printf(s, msecs_str);
+ ret = trace_seq_printf(s, "%s", msecs_str);
if (!ret)
return TRACE_TYPE_PARTIAL_LINE;

@@ -322,19 +367,15 @@ print_graph_duration(unsigned long long duration, struct trace_seq *s)

}

-/* Signal a overhead of time execution to the output */
-static int
-print_graph_overhead(unsigned long long duration, struct trace_seq *s)
+static int print_graph_abs_time(u64 t, struct trace_seq *s)
{
- /* Duration exceeded 100 msecs */
- if (duration > 100000ULL)
- return trace_seq_printf(s, "! ");
+ unsigned long usecs_rem;

- /* Duration exceeded 10 msecs */
- if (duration > 10000ULL)
- return trace_seq_printf(s, "+ ");
+ usecs_rem = do_div(t, 1000000000);
+ usecs_rem /= 1000;

- return trace_seq_printf(s, " ");
+ return trace_seq_printf(s, "%5lu.%06lu | ",
+ (unsigned long)t, usecs_rem);
}

/* Case of a leaf function on its call entry */
@@ -357,16 +398,16 @@ print_graph_entry_leaf(struct trace_iterator *iter,
duration = graph_ret->rettime - graph_ret->calltime;

/* Overhead */
- if (tracer_flags.val & TRACE_GRAPH_PRINT_OVERHEAD) {
- ret = print_graph_overhead(duration, s);
- if (!ret)
- return TRACE_TYPE_PARTIAL_LINE;
- }
+ ret = print_graph_overhead(duration, s);
+ if (!ret)
+ return TRACE_TYPE_PARTIAL_LINE;

/* Duration */
- ret = print_graph_duration(duration, s);
- if (ret == TRACE_TYPE_PARTIAL_LINE)
- return TRACE_TYPE_PARTIAL_LINE;
+ if (tracer_flags.val & TRACE_GRAPH_PRINT_DURATION) {
+ ret = print_graph_duration(duration, s);
+ if (ret == TRACE_TYPE_PARTIAL_LINE)
+ return TRACE_TYPE_PARTIAL_LINE;
+ }

/* Function */
for (i = 0; i < call->depth * TRACE_GRAPH_INDENT; i++) {
@@ -395,25 +436,17 @@ print_graph_entry_nested(struct ftrace_graph_ent_entry *entry,
struct ftrace_graph_ent *call = &entry->graph_ent;

/* No overhead */
- if (tracer_flags.val & TRACE_GRAPH_PRINT_OVERHEAD) {
- ret = trace_seq_printf(s, " ");
- if (!ret)
- return TRACE_TYPE_PARTIAL_LINE;
- }
+ ret = print_graph_overhead(-1, s);
+ if (!ret)
+ return TRACE_TYPE_PARTIAL_LINE;

- /* Interrupt */
- ret = print_graph_irq(s, call->func, TRACE_GRAPH_ENT, cpu, pid);
- if (ret == TRACE_TYPE_UNHANDLED) {
- /* No time */
+ /* No time */
+ if (tracer_flags.val & TRACE_GRAPH_PRINT_DURATION) {
ret = trace_seq_printf(s, " | ");
if (!ret)
return TRACE_TYPE_PARTIAL_LINE;
- } else {
- if (ret == TRACE_TYPE_PARTIAL_LINE)
- return TRACE_TYPE_PARTIAL_LINE;
}

-
/* Function */
for (i = 0; i < call->depth * TRACE_GRAPH_INDENT; i++) {
ret = trace_seq_printf(s, " ");
@@ -434,15 +467,30 @@ print_graph_entry_nested(struct ftrace_graph_ent_entry *entry,

static enum print_line_t
print_graph_entry(struct ftrace_graph_ent_entry *field, struct trace_seq *s,
- struct trace_iterator *iter, int cpu)
+ struct trace_iterator *iter)
{
int ret;
+ int cpu = iter->cpu;
+ pid_t *last_entry = iter->private;
struct trace_entry *ent = iter->ent;
+ struct ftrace_graph_ent *call = &field->graph_ent;

/* Pid */
- if (verif_pid(s, ent->pid, cpu) == TRACE_TYPE_PARTIAL_LINE)
+ if (verif_pid(s, ent->pid, cpu, last_entry) == TRACE_TYPE_PARTIAL_LINE)
+ return TRACE_TYPE_PARTIAL_LINE;
+
+ /* Interrupt */
+ ret = print_graph_irq(s, call->func, TRACE_GRAPH_ENT, cpu, ent->pid);
+ if (ret == TRACE_TYPE_PARTIAL_LINE)
return TRACE_TYPE_PARTIAL_LINE;

+ /* Absolute time */
+ if (tracer_flags.val & TRACE_GRAPH_PRINT_ABS_TIME) {
+ ret = print_graph_abs_time(iter->ts, s);
+ if (!ret)
+ return TRACE_TYPE_PARTIAL_LINE;
+ }
+
/* Cpu */
if (tracer_flags.val & TRACE_GRAPH_PRINT_CPU) {
ret = print_graph_cpu(s, cpu);
@@ -470,16 +518,25 @@ print_graph_entry(struct ftrace_graph_ent_entry *field, struct trace_seq *s,

static enum print_line_t
print_graph_return(struct ftrace_graph_ret *trace, struct trace_seq *s,
- struct trace_entry *ent, int cpu)
+ struct trace_entry *ent, struct trace_iterator *iter)
{
int i;
int ret;
+ int cpu = iter->cpu;
+ pid_t *last_pid = iter->private;
unsigned long long duration = trace->rettime - trace->calltime;

/* Pid */
- if (verif_pid(s, ent->pid, cpu) == TRACE_TYPE_PARTIAL_LINE)
+ if (verif_pid(s, ent->pid, cpu, last_pid) == TRACE_TYPE_PARTIAL_LINE)
return TRACE_TYPE_PARTIAL_LINE;

+ /* Absolute time */
+ if (tracer_flags.val & TRACE_GRAPH_PRINT_ABS_TIME) {
+ ret = print_graph_abs_time(iter->ts, s);
+ if (!ret)
+ return TRACE_TYPE_PARTIAL_LINE;
+ }
+
/* Cpu */
if (tracer_flags.val & TRACE_GRAPH_PRINT_CPU) {
ret = print_graph_cpu(s, cpu);
@@ -499,16 +556,16 @@ print_graph_return(struct ftrace_graph_ret *trace, struct trace_seq *s,
}

/* Overhead */
- if (tracer_flags.val & TRACE_GRAPH_PRINT_OVERHEAD) {
- ret = print_graph_overhead(duration, s);
- if (!ret)
- return TRACE_TYPE_PARTIAL_LINE;
- }
+ ret = print_graph_overhead(duration, s);
+ if (!ret)
+ return TRACE_TYPE_PARTIAL_LINE;

/* Duration */
- ret = print_graph_duration(duration, s);
- if (ret == TRACE_TYPE_PARTIAL_LINE)
- return TRACE_TYPE_PARTIAL_LINE;
+ if (tracer_flags.val & TRACE_GRAPH_PRINT_DURATION) {
+ ret = print_graph_duration(duration, s);
+ if (ret == TRACE_TYPE_PARTIAL_LINE)
+ return TRACE_TYPE_PARTIAL_LINE;
+ }

/* Closing brace */
for (i = 0; i < trace->depth * TRACE_GRAPH_INDENT; i++) {
@@ -542,14 +599,23 @@ print_graph_comment(struct print_entry *trace, struct trace_seq *s,
{
int i;
int ret;
+ int cpu = iter->cpu;
+ pid_t *last_pid = iter->private;
+
+ /* Absolute time */
+ if (tracer_flags.val & TRACE_GRAPH_PRINT_ABS_TIME) {
+ ret = print_graph_abs_time(iter->ts, s);
+ if (!ret)
+ return TRACE_TYPE_PARTIAL_LINE;
+ }

/* Pid */
- if (verif_pid(s, ent->pid, iter->cpu) == TRACE_TYPE_PARTIAL_LINE)
+ if (verif_pid(s, ent->pid, cpu, last_pid) == TRACE_TYPE_PARTIAL_LINE)
return TRACE_TYPE_PARTIAL_LINE;

/* Cpu */
if (tracer_flags.val & TRACE_GRAPH_PRINT_CPU) {
- ret = print_graph_cpu(s, iter->cpu);
+ ret = print_graph_cpu(s, cpu);
if (ret == TRACE_TYPE_PARTIAL_LINE)
return TRACE_TYPE_PARTIAL_LINE;
}
@@ -566,17 +632,17 @@ print_graph_comment(struct print_entry *trace, struct trace_seq *s,
}

/* No overhead */
- if (tracer_flags.val & TRACE_GRAPH_PRINT_OVERHEAD) {
- ret = trace_seq_printf(s, " ");
+ ret = print_graph_overhead(-1, s);
+ if (!ret)
+ return TRACE_TYPE_PARTIAL_LINE;
+
+ /* No time */
+ if (tracer_flags.val & TRACE_GRAPH_PRINT_DURATION) {
+ ret = trace_seq_printf(s, " | ");
if (!ret)
return TRACE_TYPE_PARTIAL_LINE;
}

- /* No time */
- ret = trace_seq_printf(s, " | ");
- if (!ret)
- return TRACE_TYPE_PARTIAL_LINE;
-
/* Indentation */
if (trace->depth > 0)
for (i = 0; i < (trace->depth + 1) * TRACE_GRAPH_INDENT; i++) {
@@ -614,13 +680,12 @@ print_graph_function(struct trace_iterator *iter)
case TRACE_GRAPH_ENT: {
struct ftrace_graph_ent_entry *field;
trace_assign_type(field, entry);
- return print_graph_entry(field, s, iter,
- iter->cpu);
+ return print_graph_entry(field, s, iter);
}
case TRACE_GRAPH_RET: {
struct ftrace_graph_ret_entry *field;
trace_assign_type(field, entry);
- return print_graph_return(&field->ret, s, entry, iter->cpu);
+ return print_graph_return(&field->ret, s, entry, iter);
}
case TRACE_PRINT: {
struct print_entry *field;
@@ -636,28 +701,55 @@ static void print_graph_headers(struct seq_file *s)
{
/* 1st line */
seq_printf(s, "# ");
+ if (tracer_flags.val & TRACE_GRAPH_PRINT_ABS_TIME)
+ seq_printf(s, " TIME ");
if (tracer_flags.val & TRACE_GRAPH_PRINT_CPU)
- seq_printf(s, "CPU ");
+ seq_printf(s, "CPU");
if (tracer_flags.val & TRACE_GRAPH_PRINT_PROC)
- seq_printf(s, "TASK/PID ");
- if (tracer_flags.val & TRACE_GRAPH_PRINT_OVERHEAD)
- seq_printf(s, "OVERHEAD/");
- seq_printf(s, "DURATION FUNCTION CALLS\n");
+ seq_printf(s, " TASK/PID ");
+ if (tracer_flags.val & TRACE_GRAPH_PRINT_DURATION)
+ seq_printf(s, " DURATION ");
+ seq_printf(s, " FUNCTION CALLS\n");

/* 2nd line */
seq_printf(s, "# ");
+ if (tracer_flags.val & TRACE_GRAPH_PRINT_ABS_TIME)
+ seq_printf(s, " | ");
if (tracer_flags.val & TRACE_GRAPH_PRINT_CPU)
- seq_printf(s, "| ");
+ seq_printf(s, "| ");
if (tracer_flags.val & TRACE_GRAPH_PRINT_PROC)
- seq_printf(s, "| | ");
- if (tracer_flags.val & TRACE_GRAPH_PRINT_OVERHEAD) {
- seq_printf(s, "| ");
- seq_printf(s, "| | | | |\n");
- } else
- seq_printf(s, " | | | | |\n");
+ seq_printf(s, " | | ");
+ if (tracer_flags.val & TRACE_GRAPH_PRINT_DURATION)
+ seq_printf(s, " | | ");
+ seq_printf(s, " | | | |\n");
}
+
+static void graph_trace_open(struct trace_iterator *iter)
+{
+ /* pid on the last trace processed */
+ pid_t *last_pid = alloc_percpu(pid_t);
+ int cpu;
+
+ if (!last_pid)
+ pr_warning("function graph tracer: not enough memory\n");
+ else
+ for_each_possible_cpu(cpu) {
+ pid_t *pid = per_cpu_ptr(last_pid, cpu);
+ *pid = -1;
+ }
+
+ iter->private = last_pid;
+}
+
+static void graph_trace_close(struct trace_iterator *iter)
+{
+ percpu_free(iter->private);
+}
+
static struct tracer graph_trace __read_mostly = {
.name = "function_graph",
+ .open = graph_trace_open,
+ .close = graph_trace_close,
.init = graph_trace_init,
.reset = graph_trace_reset,
.print_line = print_graph_function,
--
1.6.0.4


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